Alonso started on the hard tyres and as others pitted he rose to second place, behind only Sergio Perez, before making a late first pit stop on the same lap as the Red Bull driver.
The Spaniard was running in sixth when the rain came towards the end of the race, and finding more grip than some of his rivals he rose briefly to third again.
However he stayed out a lap too long before changing to intermediates, and any shot at a podium was lost as he slipped back to an eventual sixth place.
“It was a good race obviously for us,” he said. “The best race of the year I have to say in terms of performance. The car felt very fast, a good balance throughout the race.
“We were keeping up the pace with Checo in the first stint. Then we switched to the medium tyre, and we were able to even overtake [Max] Verstappen at one point and pull away from him.
“Then it started a little bit drizzling on dry tyres and we overtook Daniel [Ricciardo], Checo and [Carlos] Sainz and we were P3. So I think the podium was possible today on merit, the car was flying. And I was very happy, but unfortunately the rain came five laps to the end.
“Some people took some risks, some people other risks, and we were unlucky, or the podium [finishers] let’s say were very lucky today, but in these conditions it’s always a lottery.”
Asked if he was sad to lose the podium or pleased to have found performance in the car he said: “We seem ultra competitive, so we need to understand if we did something different here, try to keep [going] forward for the next events, because the car was very fast, so that was a very positive sign.
“For sure, I think we should be on the podium today in terms of executing the race and driving. We were in front of Verstappen, we were pulling away from him, we were in front of Sainz.
Fernando Alonso, Alpine A521
Photo by: Mark Sutton / Motorsport Images
“[Lando] Norris did an amazing race, and just by luck he is not on the podium or his first ever win in Formula 1. So when it rains, it’s just a very lucky factor.
“And I’m sad because when we are not competitive and we are P11 or P12, it never rains, so we never get lucky. And today that we are P3, today it just rained. So not sad. But definitely we are not very lucky.
“But every point we got this year is on merit, we never had any gifts this year. So I’m proud of every point that I took this year.”
Alpine executive director Marcin Budkowski welcomed Alonso’s result as a boost in the constructors’ championship, but added that a podium has been there for the taking had driver and team optimised the timing of the change to wet tyres.
“We’ll take sixth place, we will take the eight points, to zero to AlphaTauri and Aston Martin,” he told Autosport. “So overall in the championship we’re doing a good operation. But the silverware was on the table.
“It’s a tricky one in these conditions. It starts to rain, it can rain more or it can start raining less. It looked like it was starting to rain less, and Fernando was doing really well on his dry tyres in the tricky conditions, with light rain, passing some some cars.
“And the reality is had the rain intensity reduced he would have been P2 probably, or P1 if both [Lewis] Hamilton and Norris had pitted. But he would have been a P2.
“The rain picked up, we don’t get that right, so a bit disappointed with not finishing on the podium when we thought it was possible.
“But you can’t get it right every time. Some people got it more right than us, and some people got it less right than us.”